The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
A viewshed is an area that is visible from a fixed point of view. In computer-based map displays, a viewshed can comprise a region of the map that is visible from a particular point. A digital elevation model may be created and stored in computer-based map systems and contains elevation data for cells within a region. In standard viewshed analysis, the digital elevation model is used to determine whether a clear line of sight exists between a viewpoint cell and other target cells within the region. If a cell with a higher elevation value lies between the viewpoint cell and a target cell, then the line of sight is blocked, and the target cell is omitted from the viewshed of the viewshed cell.
Viewshed analysis for an object may be used to evaluate areas from which the object is visible, as well as to evaluate areas that are observable from the object.
Usage of a single viewshed has military and civilian applications. For example, a viewshed may be used to evaluate coverage of an existing or potential tower site, such as a radio tower, watchtower or observation point. Furthermore, viewsheds may be used for urban planning, such as to maintain the visibility of a landmark, and to evaluate the visibility of an existing or proposed building.